How to Clean a Humidifier: Vinegar, Bleach or Peroxide, Step by Step

What you need

• White vinegar. Every manual below uses it to dissolve mineral scale; Honeywell's HWM445 manual and Levoit's ask for distilled white vinegar.
• A disinfectant your manual names: household chlorine bleach for most Honeywell, Vicks and AIRCARE units, or 3% hydrogen peroxide (the drugstore strength) if the manual is silent.
• A soft brush and a soft cloth. Vicks and Honeywell warn against hard brushes and steel wool on heating elements, and CPSC says not to scratch the tank's inner surface.
• Measuring spoons and a measuring cup, because the bleach dose matters.
• Rubber gloves. Honeywell recommends them for the bleach step.

Work at a kitchen or bathroom sink on a surface that can get wet, as the Vicks and Honeywell manuals advise.

How often to clean a humidifier

From EPA's "Use and Care of Home Humidifiers", CPSC's 1992 release with the appliance makers' association (AHAM), and the makers' manuals.

When	What to do	Source
Every day	Empty the tank, wipe all surfaces dry, refill with fresh water	EPA; CPSC 1992
Every third day	Clean portable units: remove scale, deposits and film, then wipe dry	EPA
Every week	Full scale removal and disinfecting	Vicks V745, Honeywell HWM445 and Levoit Classic 300S manuals
Every 7 days (every 2 weeks for units of 5 gallons or more)	Sanitize with 1 teaspoon of bleach per gallon	CPSC and AHAM, 1992
At each wick change	Full clean of base and bottle	AIRCARE MA1201 manual
End of season	Clean, throw away the used wick or cartridge, dry every part, store dry; clean again when you bring it out	EPA; CPSC; Honeywell and AIRCARE manuals

The makers set the method; EPA sets the pace. If your manual says weekly, EPA's every third day is the more frequent of the two, and the daily empty, dry and refill does most of the work.

Step by step: cleaning a portable humidifier

1. Unplug it, empty it and let a warm mist unit cool

Every manual starts with the power off and the plug out. Vicks says to let the V745 cool for 20 to 30 minutes after use, and Honeywell says at least 20 minutes for the HWM445, so the heater is cool before you touch it. Pour out the leftover water. Vicks and Levoit both say never to put the base, which holds the motor or heater, under water.

2. Take out the wick or filter

Honeywell's HCM-350 manual says to remove the filter before scale removal or disinfecting, and that cleaning with it in place "will destroy the filter." AIRCARE has you remove and throw away the used wick each time you clean the MA1201. Levoit's Classic 300S is the exception: its small in-tank water filter comes out and soaks in vinegar along with the float.

3. Descale with white vinegar

Pour white vinegar into the tank and base (or heating chamber) in the amount your manual gives, let it stand 15 to 20 minutes, then loosen the scale with a soft brush and wipe the base with a cloth dampened in vinegar. The amounts vary by model; see the table below. CPSC's 1992 advice, written for any portable unit, is a half vinegar, half water solution with a soft brush or towel. Scale is worth removing: CPSC says it gives bacteria and fungi a surface to grow on.

4. Rinse until you cannot smell vinegar

Rinse every part with clean water until the vinegar smell is gone. Do this before you disinfect. Honeywell's HCM-350 manual says to do scale removal and disinfecting in the proper order "to avoid harmful chemical interactions," and the Vicks manual says the two steps must be performed separately.

5. Disinfect

Use your manual's method first. Honeywell's HCM-350 manual mixes 1 teaspoon of bleach with 1 gallon of cool water in the tank and uses the same solution to wipe the base. Vicks uses 1 teaspoon per gallon in the tank and heating chamber for 20 minutes, and Honeywell's HWM445 uses half a teaspoon in half a gallon, the same strength, for 20 minutes. Vicks warns that using more than 1 teaspoon per gallon "will result in damage to your humidifier."

If the manual gives no method, EPA's advice is to clean every surface that touches water with a 3% hydrogen peroxide solution. Levoit's Classic 200 manual also allows 3% hydrogen peroxide in place of vinegar and says never to mix the two. Children's Hospital of Philadelphia suggests a much stronger soak for most devices, 1 part bleach to 9 parts water; where a manual sets a lower dose and says more will damage the unit, follow the manual.

6. Rinse again, dry and put it back together

EPA says to rinse with several changes of tap water after any cleaning or disinfecting agent, so no chemicals are released into the air when the unit runs, and CPSC gives the same warning for bleach. Rinse until you cannot smell bleach, dry the parts with a clean cloth, fit a fresh or rinsed wick and refill. Levoit's Classic 200 manual adds one more rule: do not run the humidifier immediately after disinfecting it.

Vinegar, bleach or hydrogen peroxide: what each one does

From EPA, CPSC, the Washington State Department of Health and the makers' manuals.

Agent	Job	Who names it	Watch for
White vinegar	Dissolves mineral scale	Every manual here; CPSC 1992	It is an acid: never mix it with bleach
Chlorine bleach	Disinfects	Honeywell, Vicks and AIRCARE manuals; CPSC 1992 (1 teaspoon per gallon)	More than the manual's dose damages Vicks and Honeywell units; stains fabric. EPA's humidifier page does not mention bleach
3% hydrogen peroxide	Disinfects	EPA, when the maker gives no method; Levoit Classic 200 manual	Never mix it with vinegar (Levoit) or bleach
Dishwasher	Cleans the parts a manual lists	Vicks V745 and Honeywell HWM445 manuals (small parts); the HCM-350 manual (tank)	Vicks and the HWM445: top rack, below 158°F (70°C), no detergent. Levoit says no Classic 300S part goes in a dishwasher

The mixing rules come from chemistry, not brand preference. The Washington State Department of Health says chlorine bleach mixed with an acid such as vinegar gives off chlorine gas, bleach mixed with ammonia makes toxic chloramines, and bleach also reacts with hydrogen peroxide. Use one product, rinse it out, then use the next.

What each maker's manual says

From each maker's owner's manual. Another model from the same brand can differ, so check the manual for yours.

Model (type)	Descale	Disinfect	Dishwasher	How often
Honeywell HCM-350 (evaporative)	Wipe base, tank cap and tank with undiluted vinegar; rinse	1 tsp bleach in 1 gal cool water in the tank; wipe the base with it; rinse	Tank yes; tank cap no	Regularly; replace the Protec cartridge after 30 days of regular use
Vicks V745 (warm mist)	1 cup vinegar in tank and heating chamber, 20 min; soft brush on the heater	1 tsp bleach per gal, 20 min	Medicine cup, tray and mist chimney only, top rack, no detergent	Rinse daily; clean weekly
Honeywell HWM445 (warm mist)	3 cups undiluted distilled white vinegar, 20 min; soft brush on the heater	1/2 tsp bleach in 1/2 gal water, 20 min	Top cover, mist chimney and heating element cover, top rack, no detergent	Weekly
AIRCARE MA1201 (console evaporative)	Base and bottle half full of water plus 1 cup vinegar each, 20 min	Base and bottle half full of water plus 1 tsp bleach each, 20 min	None named	At every wick change
Levoit Classic 300S (ultrasonic)	3 cups distilled white vinegar in the tank, 15 to 20 min; soak float, filter and silencer in vinegar	No bleach step in the manual	No part	Weekly and before storage; change the water daily

How to clean a Vicks humidifier

For the Vicks V745 warm mist humidifier, the manual's daily routine is to unplug it, let it cool at least 20 minutes, drain the tank, rinse it with lukewarm water and wipe the heater and heating chamber with a soft, damp cloth. Weekly, soak the tank and heating chamber in 1 cup of vinegar for 20 minutes, scrub the heating element gently with a soft brush, wipe the other parts with undiluted white vinegar and rinse, using no soap, detergents or abrasive cleaners. Then disinfect with 1 teaspoon of bleach per gallon for 20 minutes and rinse until the smell is gone. Vicks also says not to put essential oils or medications such as VapoSteam into the tank, base or reservoir.

How to clean a Levoit humidifier

Levoit's US manual for the Classic 300S says to clean it every week and before storing it, to change the water daily, and never to use detergents, immerse the base or put any part in a dishwasher. The steps: rinse the tank cover, take out the water filter, and rinse the tank, filter and base chamber with room-temperature water. Fill the tank with 3 US cups (710 mL) of distilled white vinegar, swish it, and set the tank on the base for 15 to 20 minutes so the vinegar drains into the base and loosens scale on the transducer and float. Pour it out, soak the float, filter and noise silencer in vinegar for 15 to 20 minutes, brush off the scale with the cleaning brush, rinse until the vinegar smell is gone and dry everything before reassembling. Other Levoit models have their own manuals; follow yours.

Getting mold or slime out of a humidifier

CPSC says film or scum on the water, on the tank walls or on exposed motor parts may mean the tank holds bacteria or fungi. Clean it with the full routine above, in order: throw away the wick (or rinse a reusable one), descale, rinse, disinfect with your manual's method and brush every surface you can reach without damaging the motor. If growth comes back within days, or sits in channels you cannot reach, replace the humidifier.

EPA advises that if you have respiratory symptoms you believe are linked to using your humidifier, stop using it and contact your physician, even if you have followed the maintenance directions. For why mold grows in the first place and how room humidity feeds it, see humidifier mold prevention.

Wicks, filters and cartridges

Evaporative wicks are not cleaned with chemicals. Honeywell's answer for an HCM-350 wick that has turned light brown is that the color is a mineral deposit: soak it in a sink of cool water to break up the deposits. Replace it on the maker's schedule. Honeywell's store says Filter A should be replaced every 30 to 60 days depending on water quality and use, sooner with very hard water, and AIRCARE says to replace the MA1201's wick at least once a season, more often depending on your water. Genuine replacements: Honeywell Filter A for the HCM-350 series, AIRCARE MAF1 for the MA1201, and Vornado MD1-0034 for the EVDC500.

Demineralization cartridges in ultrasonic units are a different part. EPA says their ability to remove minerals may vary widely, that "white dust" means minerals are getting through, and that used cartridges should be thrown away. Honeywell says to replace the HCM-350's Protec antimicrobial cartridge after 30 days of regular use.

Some makers add a bacteriostat to the water. AIRCARE recommends its Essick Air Bacteriostat Treatment (part 1970) at each refill of the MA1201, says to use only an EPA-registered bacteriostat, and says never to use treatments made for Rotobelt or ultrasonic humidifiers. The product's EPA registration notice and label (EPA Reg. No. 81371-1, 2005) describe it for the water tanks of manually filled evaporative humidifiers and carry a DANGER warning (corrosive; causes irreversible eye damage and skin burns), with goggles or a face shield and rubber gloves required. Follow the dose and warnings on the bottle you buy. It does not replace cleaning.

Whole-house (furnace) humidifiers

EPA says to follow the maker's directions for console and furnace-mounted humidifiers. Resideo's HE360 manual is typical of a bypass unit: every 1 to 3 months, depending on water quality, disconnect the power and shut off the water supply, take out the pad assembly, remove mineral deposits from the tray and frame, make sure the drain hole is clear, flush the drain hose with a running tap and fit a new pad with its marked end up. Resideo notes that hard-water deposits are harder to clean and says never to oil any part.

For AprilAire, the owner FAQ says the water panel in Models 300, 500, 600 and 700 is replaced every humidifier season, the Model 400's every 3 months, and the Model 400's scale control insert, floats and float chambers are cleaned twice a season. If you would rather not open a unit on the ductwork, have it done with the furnace's annual service.

Mistakes that damage a humidifier

• Mixing cleaners. Bleach with vinegar gives off chlorine gas, and bleach reacts with ammonia and hydrogen peroxide (Washington State Department of Health).
• Extra bleach. Vicks and Honeywell both warn that more than their stated dose damages the humidifier.
• Soap and detergent. Vicks says no soap, detergents or abrasive cleaners; Levoit says no detergents; dishwasher-cleaned parts go in without detergent.
• Steel wool on a heater. Honeywell says hard brushes or steel wool damage the HWM445's protective coating and cause the heating element to fail.
• Water in the base. Vicks and Levoit say never to immerse it.
• Additives in the tank. Vicks and Honeywell forbid essential oils and inhalants in the water; the HWM445 and Levoit's Classic models take oils only in a separate cup or pad.
• A quick rinse. EPA says several changes of water, so the disinfectant does not end up in the mist.
• Storing it wet. EPA says to dry every part before storage; Vicks adds to leave the tank cap partly loosened, and AIRCARE says not to store the MA1201 in an attic or other hot space.

Making the next clean easier

Water choice sets how much scale you remove. CPSC recommends distilled or demineralized water to reduce scale and white dust, and Vicks says tap-water minerals stick to the heater and impair it. See distilled vs tap water in a humidifier. The type matters too: evaporative units keep minerals in the wick and ultrasonic units put them in the air, as covered in ultrasonic vs evaporative humidifiers. For units with wide tanks and few parts, see the best humidifiers; for a child's room, baby humidifier safety.